This invention relates to oil sumps for vertically shafted engines, and to adapting outboard marine motor engines for use in marine generator sets.
Outboard marine motors have been developed over several decades to become a mature technology, with commercially available units mass produced by various manufacturers to be cost-effective means for driving propellers on small to medium sized watercraft. The typical outboard marine motor has a gas-powered engine operating on either a two-stroke or four-stroke combustion cycle to turn a vertical crankshaft that extends below the water line to engage and drive a propeller. The engine is commonly encased in a housing that encloses the engine and provides means for mounting the motor outboard of the transom of a boat. The housing also generally supports the drive shaft between engine and propeller, provides a sump for lubricating oil (in the case of four-stroke engines), and ports exhaust gases and cooling seawater downward from the engine.
Although such motors have been available for several years, their use on boats has generally been limited to their primary intended application: turning propellers. I have realized that engines from such motors can be usefully modified to drive on-board electrical generators, and have filed a provisional patent application on Nov. 7, 2000, entitled xe2x80x9cElectrical Power Generation, serial No. 60/246,554, the entire contents of which are hereby incorporated by reference as if entirely set forth.
The present invention features an improved oil sump useful for such modification.
According to one aspect of the invention, an oil sump for a vertically shafted combustion engine has a housing with an upper face for sealing against a block of the engine. The sump housing defines an internal volume for containing a quantity of oil received from the engine through an oil drain opening in the upper face of the sump, and defines an exhaust inlet for receiving a flow of exhaust from the engine and directing the flow of exhaust toward an exhaust outlet along an exhaust passage defined within the housing. The sump housing also defines a water inlet for receiving a flow of cooling water into a water passage defined within the housing about the exhaust passage for cooling the flow of exhaust.
In another aspect, the present invention features an improved, combination oil sump and engine mount useful for modifying an outboard motor engine for use in other applications. In this aspect, the sump housing further comprises means for securely mounting the engine within a boat hull. In some cases, the mounting means include one or more mounting holes for receiving removable fasteners for securely mounting the engine within a boat hull. The mounting holes can be through holes defined in lugs extending from the sump housing, or blind and tapped holes extending into the sump housing.
The alternator or generator may be of several types known in the art, but for some applications a variable speed, permanent magnet alternator is preferred. Such alternators are commonly used in generating electrical power from wind-driven turbines, for example, and can be equipped with power conditioning circuitry to provide a stable output frequency over a wide range of input speeds. An advantage of variable speed operation is that the engine can be configured to change speeds in response to load, to maintain an optimum operating efficiency and to enable the use of advantageously small, less powerful engines.
By xe2x80x9crotorxe2x80x9d I mean the rotating portion of the alternator, whether carrying electrical windings as an armature, or carrying magnets.
In some embodiments, the permanent magnet alternator is coupled to the engine to run at a relatively constant, xe2x80x9csynchronousxe2x80x9d speed (e.g., 1800 RPM), to produce a desired output frequency. Such a configuration is appropriate for applications that will accommodate some variation in output voltage over a range of operational loads and temperatures. One advantage of this configuration is that it employs a much simpler alternator architecture than that of a wound generator stator with exciter circuits, for example, without the added expense of solid state frequency generation circuitry.
According to another aspect of the invention, a method of producing electrical power on-board a boat is provided. The method includes the steps of attaching the above-described oil sump to the block of an outboard motor engine, attaching the crankshaft of the engine to an electrical generator, mounting the engine and generator on-board a boat, and running the engine to produce electrical power, and directing electrical power from the generator to a remote electrical load, such as an electrical appliance or on-board power grid, to perform useful work.
According to another aspect of the invention, a method of modifying a vertically shafted outboard motor engine is provided. The method includes the step of mounting the above-described sump to a lower face of the engine. In some embodiments, a pulley is attached to the exposed end of the engine crankshaft within the vertical profile of the sump, for driving a vertically-shafted alternator.
The sump housing is preferably very low profile, such as less than about five inches deep (more preferably, less than about 3.5 inches deep), in order to package the engine and sump within typical low overhead spaces. The sump also provides side clearance to the engine crankshaft for belting or otherwise side-coupling the crankshaft to the alternator rotor in a side-by-side mounting arrangement, preferably within the vertical profile of the sump itself, or to other belt-driven devices such as a seawater pump.
Preferably, the internal volume of the sump accommodates an oil volume at least as large as the volume of oil accommodated by the outboard motor housing in which the engine was designed to be packaged. In many cases, the sump should accommodate at least about 60 cubic inches of engine oil.
This invention can facilitate the use of conventional outboard motor engines in applications for which such engines were not intended when designed and manufactured. Particularly, this invention facilitates the mounting of such engines on-board boats, rather than in outboard motor housings, and the coupling of such engines to electric alternators for the generation of useful electrical energy rather than the turning of a propeller. In many applications, this advantageous conversion of outboard motor engines is accomplished without any substantive modification of the engine""s internal components or block, thereby maintaining the high reliability that such engines have been designed to achieve. The resulting engine-generator set can provide cost-effective electrical power generators of a physical size and power rating particularly needed by some boat owners, particularly those with moderate to low power requirements and who prefer a system that can be permanently mounted below deck and out of sight, rather than mounted outboard, exposed to direct salt spray and less secure from theft.
Some aspects of the invention can provide for the ready modification of outboard motor engines for use in running electrical generators, without having to modify any principal engine components or compromise engine structural rigidity. The sump can be mounted directly to the lower face of the engine block in place of a standard oil sump, employing a gasket or other type of face seal to the lower edge of the block. The sump can be made to accommodate a desired oil volume, with appropriately placed drain passages from the engine block for recirculating the engine oil. The improved sump can also be provided with structural mounting bosses to secure the engine to a frame mounted within a boat hull. The sump can direct a flow of seawater or other cooling water about the exhaust coming from the engine, to cool the exhaust to more manageable temperatures before the exhaust leaves the sump, where the exhaust and water streams can be joined for further exhaust cooling. Internal porting of the seawater can also be made to cool the lubricating oil housed within the sump, and to insulate the lubricating oil from the heat of the exhaust.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.